Introduction

By default, Ubuntu systems run with the Ubuntu kernels provided by the Ubuntu repositories. However it is handy to be able to test with unmodified upstream kernels to help locate problems in the Ubuntu kernel patches, or to confirm that upstream has fixed a specific issue. To this end we now offer select upstream kernel builds. These kernels are made from unmodified kernel source but using the Ubuntu kernel configuration files. These are then packaged as Ubuntu .deb files for simple installation.

These kernels are not supported and are not appropriate for production use.

Upstream kernels archive

The upstream kernels archive is located at the URL below. There is a directory for each build. Note, if you are testing for a bug, please do not use the daily folder, but use the latest mainline kernel at the top:

The tagged releases (as made by Linus and the stable maintainers) are found under a directory matching their tag name and which kernel configuration they were built with (<tag>-<series>). Daily tip of the tree builds are found in the daily sub-directory named for the date they were made.

Each build directory contains the header and image .deb files for the generic flavour i386 and amd64 architectures.

Preparing to install an upstream kernel

First, if one is using select proprietary or out-of-tree modules (ex. vitualbox, nvidia, fglrx, bcmwl, etc.) unless there is an extra package available for the version you are testing, you will need to uninstall the module first, in order to test the mainline kernel. If you do not uninstall these modules first, then the upstream kernel more than likely will not boot.

Installing upstream kernels (manually)

To boot into an upstream kernel you need to download and install the packages that corresponds to your architecture.

It is best to download the files into a folder by themselves. Also, it is recommended to verify the integrity of downloaded packages as explained below under "Verifying the mainline build binaries".

Then, one may install all the packages simultaneously by executing the following in a terminal:

sudo dpkg -i *.deb

When this process completes you should have a new entry on your boot menu representing the upstream kernel (press Shift while booting if your boot menu doesn't show). This will appear as an entry like this:

Ubuntu Trusty, kernel 3.14.4-031404-generic

The headers-<kernelname>_<architecture>.deb and headers-<kernelname>_all.deb packages allow one to build external modules.

Problems installing the upstream kernel

Some have found issues installing an upstream kernel due to an error. For example:

This is due to how one did not follow the previous directions of uninstalling out-of-tree modules, in this case virtualbox.

Uninstalling upstream kernels

The upstream kernels have their own ABI namespace, so they install side by side with the stock Ubuntu kernels (each kernel has a separate directory under /lib/modules/VERSION for example). This means that you can keep several mainline and Ubuntu stock kernels installed at the same time and select the one you need from the GRUB boot menu.

If you would like to uninstall an upstream kernel anyway, execute the following to find the exact name of the kernel packages you want to uninstall:

dpkg -l | grep "linux\-[a-z]*\-"

and then execute the following to uninstall them:

sudo apt-get remove KERNEL_PACKAGES_TO_REMOVE

Remember that several packages can belong to one kernel version: common headers, architecture specific headers and the architecture specific image.

Also, once the mainline packages are removed, one may still see entries for these via the above dpkg command. To purge these entries execute at a terminal:

sudo dpkg --purge ENTRY

Mainline build tool chain

These kernels are built with the tool chain (gcc etc.) from the previous LTS (Ubuntu 8.04/10.04/12.04) depending on version. Therefore, out-of-tree kernel modules built with tools from other versions likely will not work. The file BUILD in later mainline builds details what was used.

Mainline kernel mapping to Ubuntu kernel

The Ubuntu kernel is not bit-for-bit the same as the mainline. However, one may find the upstream release that the Ubuntu kernel is based on via the Ubuntu to mainline mapping table.

Does the kernel team support the mainline kernel builds?

The mainline kernel builds are produced for debugging purposes and therefore come with no support. Use them at your own risk.

Where can I get the source for these builds?

In each directory there is a COMMIT file which defines the base commit in Linus' master tree from which they were built. The patches in the same directory ????-* are applied on top of this commit to make the build tree. A mirror of Linus' tree is available from git://kernel.ubuntu.com/virgin/linux.git.

First download the COMMIT and patch files ????-* from the mainline build in question to a temporary directory:

Verifying the mainline build binaries

In order to allow verification that the published builds are the builds made by the mainline build system, the individual files are checksummed and the results of that published as CHECKSUMS in the same directory. This file is in turn signed by the mainline builder using the GPG key below which can be obtained from the Ubuntu Keyserver:

Download the CHECKSUMS and CHECKSUMS.gpg files from the build directory and verify if the CHECKSUMS is signed with the above key:

$ gpg --verify CHECKSUMS.gpg CHECKSUMS
gpg: Signature made .... using RSA key ID 17C622B0
gpg: Good signature from "Kernel PPA <kernel-ppa@canonical.com>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg: There is no indication that the signature belongs to the owner.

Verify the checksums of downloaded deb files:

$ shasum -c CHECKSUMS 2>&1 | grep 'OK$'

You should get a line ending with "OK" for each of downloaded deb file and each type of checksums that are given in the CHECKSUMS file.

Upstream kernels in detail

We currently build five sets of upstream kernels. All formal tags from Linus' tree and from the stable trees, plus: